perf/x86: Fix missing sample size update on AMD BRS

It missed to convert a PERF_SAMPLE_BRANCH_STACK user to call the new
perf_sample_save_brstack() helper in order to update the dyn_size.
This affects AMD Zen3 machines with the branch-brs event.

Fixes: eb55b45 ("perf/core: Add perf_sample_save_brstack() helper")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20230427030527.580841-1-namhyung@kernel.org

arch/x86/events/core.c

@@ -1703,10 +1703,8 @@ int x86_pmu_handle_irq(struct pt_regs *regs)
 
 		perf_sample_data_init(&data, 0, event->hw.last_period);
 
-		if (has_branch_stack(event)) {
-			data.br_stack = &cpuc->lbr_stack;
-			data.sample_flags |= PERF_SAMPLE_BRANCH_STACK;
-		}
+		if (has_branch_stack(event))
+			perf_sample_save_brstack(&data, event, &cpuc->lbr_stack);
 
 		if (perf_event_overflow(event, &data, regs))
 			x86_pmu_stop(event, 0);